A Couple Conversion Questions
 

First of all, could a 2wd be converted to a 6 lug pattern?

Second, would the whole rear axle from a 99+ truck fit under my 84? I think it would be pretty neat to have the disc brakes, plus i have a friend that deals in wrecked cars that could probably find me one. If it would fit, what might i have to do to the brake system for everything to work right?

the 70 and pre trucks were 6 lug. i dont think the axle would fit without some modification. may not be the same width, and the spring perches would have to be redone. probably among other things.

yes, a 2wd can be converted to 6 lug. install a pair of 1/2 ton rear axle shafts in your existing axle. you'll also have to getthe drums, and possibly the backing plates too. then, from the same donor truck, remove the front axle, trans, and transfer case, and complete steering/suspension setup, along with any brackets that you may need to mount said steering/suspension. convert it to a *REAL* truck. :D